I do not drive a BA but some straight forward mods you could do would be to switch to
lighter seats and
wheels. Move the battery to the boot and switch it to an
Optima unit Not just weight savings but improved balance there. I saw a carbon fibre boot advertised from the same people who do the bonnets.
More difficult but ultimately more telling would be to switch to an alloy block. Perhaps a modified brake system using the
DBA 5000 series lightweight two piece discs and some
Wilwood Billet Dynalite calipers? Always nice to reduce unsprung weight. Might also be some advantage to be had switching to a coilover setup although costly for a decent threaded type.